The biceps brachii, which is composed of a short head and a long head, and the brachialis, and triceps brachii, composed of a long head, a lateral head, and a medial head, are the main muscles of the arm. The biceps brachii and brachialis are at the front of the arm, and both are flexors of the elbow. The triceps brachii muscle group is at the back of the arm, and is an an extensor of the elbow. To stretch each of these muscles, you need a movement that is opposite to the function of each muscle. To stretch the biceps brachii and brachialis, you need to extend your elbow. To stretch your triceps brachii, you need to flex your elbow.

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About the Author

Richard Choueiri is a fitness and nutrition expert and the author of "The Human Statue Workout." He began writing professionally in 2007 and his work has been featured in Bodybuilding.com and "Physique Magazine." Choueiri studied exercise science and nutritional science at Rutgers University. He holds an American College of Sports Medicine CPT, and a National Exercise and Sports Trainers Association CMMACC.